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VWO Feature Management and Experimentation SDK for PHP

Overview

The VWO Feature Management and Experimentation SDK (VWO FME Php SDK) enables php developers to integrate feature flagging and experimentation into their applications. This SDK provides full control over feature rollout, A/B testing, and event tracking, allowing teams to manage features dynamically and gain insights into user behavior.

Requirements

• PHP 7.0 and onwards

Installation

Install the latest version with

Basic Usage Example

The following example demonstrates initializing the SDK with a VWO account ID and SDK key, setting a user context, checking if a feature flag is enabled, and tracking a custom event.

Advanced Configuration Options

To customize the SDK further, additional parameters can be passed to the init() API. Here's a table describing each option:

Refer to the official VWO documentation for additional parameter details.

User Context

The context array uniquely identifies users and is crucial for consistent feature rollouts. A typical context includes an id for identifying the user. It can also include other attributes that can be used for targeting and segmentation, such as customVariables, userAgent and ipAddress.

Parameters Table

The following table explains all the parameters in the context array:

Example

Basic Feature Flagging

Feature Flags serve as the foundation for all testing, personalization, and rollout rules within FME. To implement a feature flag, first use the getFlag API to retrieve the flag configuration. The getFlag API provides a simple way to check if a feature is enabled for a specific user and access its variables. It returns a feature flag object that contains methods for checking the feature's status and retrieving any associated variables.

Example usage:

Custom Event Tracking

Feature flags can be enhanced with connected metrics to track key performance indicators (KPIs) for your features. These metrics help measure the effectiveness of your testing rules by comparing control versus variation performance, and evaluate the impact of personalization and rollout campaigns. Use the trackEvent API to track custom events like conversions, user interactions, and other important metrics:

Example usage:

See Tracking Conversions documentation for more information.

Pushing Attributes

User attributes provide rich contextual information about users, enabling powerful personalization. The setAttribute method provides a simple way to associate these attributes with users in VWO for advanced segmentation. Here's what you need to know about the method parameters:

Example usage:

Or

See Pushing Attributes documentation for additional information.

Generating UUID

The getUUID method allows you to generate a UUID that gets stored on VWO by providing a userId and accountId. This UUID is generated using a deterministic algorithm based on the user and account identifiers, ensuring consistent UUID generation for the same user-account combination.

Return Value

Returns a UUID string formatted without dashes and in uppercase (e.g., 'CC25A368ADA0542699EAD62489811105').

Example Usage

Custom Bucketing Seed

By default, the SDK uses the user's id to determine which variation or feature a user is bucketed into. The bucketingSeed parameter lets you override this behavior by providing a custom string for bucketing calculations.

This is useful when you want to:

• Ensure consistent bucketing across different user identifiers or SDKs
• Group different users into the same bucket by using a shared seed

Polling Interval Adjustment

The pollInterval is an optional parameter that allows the SDK to automatically fetch and update settings from the VWO server at specified intervals. Setting this parameter ensures your application always uses the latest configuration.

Gateway

The VWO FME Gateway Service is an optional but powerful component that enhances VWO's Feature Management and Experimentation (FME) SDKs. It acts as a critical intermediary for pre-segmentation capabilities based on user location and user agent (UA). By deploying this service within your infrastructure, you benefit from minimal latency and strengthened security for all FME operations.

Why Use a Gateway?

The Gateway Service is required in the following scenarios:

• When using pre-segmentation features based on user location or user agent.
• For applications requiring advanced targeting capabilities.
• It's mandatory when using any thin-client SDK (e.g., Go).

How to Use the Gateway

The gateway can be customized by passing the gatewayService parameter in the init configuration.

Refer to the Gateway Documentation for further details.

Proxy

The proxy parameter allows you to redirect all SDK network calls through a custom proxy URL. This feature enables you to route all SDK network requests (settings, tracking, etc.) through your own proxy server, providing better control over network traffic and security.

The proxy object accepts the following parameters:

Synchronous network calls

Synchronous network calls differ from the default (asynchronous or fire-and-forget) tracking behavior by waiting for the tracking request to return a response from the VWO server before proceeding with the rest of your application code. By default, the SDK sends tracking network calls in a way that does not block your application, providing maximum throughput and lowest latency for user actions.

Why is it so?

• The default asynchronous approach ensures minimal impact on user experience or application response times. Tracking calls are dispatched without waiting for a server response.
• With synchronous calls enabled (shouldWaitForTrackingCalls => true), your code will block and wait for the network call to complete, allowing you to detect network errors, retry, and ensure delivery before execution continues.

When should you use synchronous calls?

• Use synchronous tracking when tracking data integrity or acknowledgment is critical before user flow continues (e.g., checkout flows, conversion confirmations, or compliance events).
• It is recommended when you need to guarantee that server-side events are delivered, and are willing to trade a slight increase in user-facing latency for this assurance.

You can opt-in to perform network calls synchronously by passing an init parameter.

Notes:

• In PHP, the default transport for tracking is a non-blocking socket-based call (fire-and-forget).
• When you enable shouldWaitForTrackingCalls, the SDK switches to a blocking cURL-based call so your code waits for the response.
• For synchronous (cURL) calls, retry is enabled by default. You can override via retryConfig in init:

If you want synchronous calls but without retries, set shouldRetry to false:

Storage

The SDK operates in a stateless mode by default, meaning each getFlag call triggers a fresh evaluation of the flag against the current user context.

To optimize performance and maintain consistency, you can implement a custom storage mechanism by passing a storage parameter during initialization. This allows you to persist feature flag decisions in your preferred database system (like Redis, MongoDB, or any other data store).

Key benefits of implementing storage:

• Improved performance by caching decisions
• Consistent user experience across sessions
• Reduced load on your application

The storage mechanism ensures that once a decision is made for a user, it remains consistent even if campaign settings are modified in the VWO Application. This is particularly useful for maintaining a stable user experience during A/B tests and feature rollouts.

Logger

VWO by default logs all ERROR level messages to your server console. To gain more control over VWO's logging behaviour, you can use the logger parameter in the init configuration.

Example 1: Set log level to control verbosity of logs

Example 2: Add custom prefix to log messages for easier identification

Example 3: Enable ANSI color codes for colored log levels in terminal

Note: ANSI color codes are only applied when isAnsiColorEnabled is explicitly set to true. This prevents unwanted color codes in log files or non-terminal outputs. When disabled or not set, log levels are displayed as plain text.

Example 4: Implement custom transport to handle logs your way

The transport parameter allows you to implement custom logging behavior by providing your own logging functions. You can define handlers for different log levels (debug, info, warn, error, trace) to process log messages according to your needs.

For example, you could:

• Send logs to a third-party logging service
• Write logs to a file
• Format log messages differently
• Filter or transform log messages
• Route different log levels to different destinations

The transport object should implement handlers for the log levels you want to customize. Each handler receives the log message as a parameter.

For single transport you can use the transport parameter. For example:

For multiple transports you can use the transports parameter. For example:

Integrations

VWO FME SDKs provide seamless integration with third-party tools like analytics platforms, monitoring services, customer data platforms (CDPs), and messaging systems. This is achieved through a simple yet powerful callback mechanism that receives VWO-specific properties and can forward them to any third-party tool of your choice.

User Aliasing

User aliasing lets you associate an existing user ID with an alternate ID (alias) so future evaluations and tracking use a unified identity across systems.

Requirements:

• Gateway must be configured
• Aliasing must be enabled during initialization: isAliasingEnabled: true

Initialization example:

Usage examples:

Behavior and validations:

• Returns true on success, false otherwise
• Requires aliasing to be enabled and gateway configured
• aliasId must be a non-empty string (not an array); it is trimmed before use
• When passing context, context['id'] must be a non-empty string (not an array); it is trimmed before use
• userId and aliasId cannot be the same

Version History

The version history tracks changes, improvements, and bug fixes in each version. For a full history, see the CHANGELOG.md.

Development and Testing

1. Set development environment

2. Run test cases

Contributing

Please go through our contributing guidelines

Code of Conduct

Code of Conduct

License

Apache License, Version 2.0

Copyright 2024-2026 Wingify Software Pvt. Ltd.